It's incredibly difficult to build a sticky product. Similar to email, browser notifications can be an extremely effective way to bring people back to the site. I'm surprised more product builders aren't using them.

OneSignal is the most knowledgeable vendor in the push space. It’s not just notifications, but you have to know what’s happening in the browser landscape. I always learn a lot from my conversations with them and I didn’t get the same impression from other vendors.